Apparatus for transmitting and receiving a signal and method of transmitting and receiving a signal

ABSTRACT

According to one embodiment, a transmitter for transmitting at least one broadcast signal having PLP (Physical Layer Pipe) data includes: a BCH (Bose-Chadhuri-Hocquenghem) encoder configured to BCH encode the PLP data; an LDPC (Low Density Parity Check) encoder configured to LDPC encode the BCH encoded PLP data and output FECFrames (Forward Error Correction Frames); a mapper configured to map data in the FECFrames onto constellations by QAM (Quadrature Amplitude Modulation) schemes; a time-interleaver configured to time-interleave the mapped data; a frame builder configured to build a signal frame including preamble symbols and data symbols; and an OFDM (Orthogonal Frequency Division Multiplexing) modulator configured to modulate data in the signal frame by an OFDM scheme. The PLP data are processed by an LDPC scheme for a long or a short LDPC FECframe. The preamble symbols include signaling information for the time-interleaved PLP data. The data symbols include the time-interleaved PLP data.

TECHNICAL FIELD

The present invention relates to a method for transmitting and receivinga signal and an apparatus for transmitting and receiving a signal, andmore particularly, to a method for transmitting and receiving a signaland an apparatus for transmitting and receiving a signal, which arecapable of improving data transmission efficiency.

BACKGROUND ART

As a digital broadcasting technology has been developed, users havereceived a high definition (HD) moving image. With continuousdevelopment of a compression algorithm and high performance of hardware,a better environment will be provided to the users in the future. Adigital television (DTV) system can receive a digital broadcastingsignal and provide a variety of supplementary services to users as wellas a video signal and an audio signal.

Digital Video Broadcasting (DVB)-C2 is the third specification to joinDVB s family of second generation transmission systems. Developed in1994, today DVB-C is deployed in more than 50 million cable tunersworldwide. In line with the other DVB second generation systems, DVB-C2uses a combination of Low-density parity-check (LDPC) and BCH codes.This powerful Forward Error correction (FEC) provides about 5 dBimprovement of carrier-to-noise ratio over DVB-C. Appropriatebit-interleaving schemes optimize the overall robustness of the FECsystem. Extended by a header, these frames are called Physical LayerPipes (PLP). One or more of these PLPs are multiplexed into a dataslice. Two dimensional interleaving (in the time and frequency domains)is applied to each slice enabling the receiver to eliminate the impactof burst impairments and frequency selective interference such as singlefrequency ingress.

DISCLOSURE OF INVENTION Technical Problem

With the development of these digital broadcasting technologies, arequirement for a service such as a video signal and an audio signalincreased and the size of data desired by users or the number ofbroadcasting channels gradually increased.

Technical Solution

Accordingly, the present invention is directed to a method fortransmitting and receiving a signal and an apparatus for transmittingand receiving a signal that substantially obviate one or more problemsdue to limitations and disadvantages of the related art.

An object of the present invention is to provide a transmitter oftransmitting at least one broadcasting signal having PLP (Physical LayerPipe) data to a receiver, comprising: an LDPC FEC Encoder configured toLDPC encode the PLP data and output FECFrame; a mapper configured toconvert the FECFrame to XFECFrame by QAM constellation; aFEC-Frame-Header-Insertion configured to insert FECFrame header in frontof the XFECFrame; a data slice builder configured to output at least onedata slice based on the XFECFrame and the FECFrame header; atime-interleaver configured to perform time-interleaving at a level ofthe data slice; and a frequency-interleaver configured tofrequency-interleave the time-interleaved data slice.

Another aspect of the present invention provides a receiver of receivingat least one broadcasting signal having PLP(Physical Layer Pipe),comprising: a frequency-deinterleaver configured tofrequency-deinterleave the received signal; a time-deinterleaverconfigured to time-deinterleave the frequency-deinterleaved signal at alevel of the data slice; a data slice parser configured to output dataslice packets of PLP from the data slice, the data slice packetincluding header; a FEC-Frame-Header-Extractor configured to obtain theheader from the data slice packet; and a decoder configured to decodethe data slice packets by LDPC(low density parity check) scheme.

Yet another aspect of the present invention provides a method oftransmitting at least one broadcasting signal having PLP(Physical LayerPipe) data to a receiver, comprising: LDPC-encoding the PLP data andoutputting FECFrame; mapping the FECFrame to XFECFrame by QAMconstellation; inserting FECFrame header in front of the XFECFrame;building at least one data slice based on the XFECFrame and the FECFrameheader; time-interleaving at a level of the data slice; andfrequency-in-terleaving the time-interleaved data slice.

Yet another aspect of the present invention provides a method ofreceiving at least one broadcasting signal having PLP(Physical LayerPipe), comprising: frequency-deinterleaving the received signal;time-deinterleaving the frequency-deinterleaved signal at a level of thedata slice; outputting data slice packets of PLP from the data slice,the data slice packet including header; obtaining the header from thedata slice packet; decoding the data slice packets by LDPC(low densityparity check) decoding scheme.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is an example of 64-Quadrature amplitude modulation (QAM) used inEuropean DVB-T.

FIG. 2 is a method of Binary Reflected Gray Code (BRGC).

FIG. 3 is an output close to Gaussian by modifying 64-QAM used in DVB-T.

FIG. 4 is Hamming distance between Reflected pair in BRGC.

FIG. 5 is characteristics in QAM where Reflected pair exists for each Iaxis and Q axis.

FIG. 6 is a method of modifying QAM using Reflected pair of BRGC.

FIG. 7 is an example of modified 64/256/1024/4096-QAM.

FIGS. 8-9 are an example of modified 64-QAM using Reflected Pair ofBRGC.

FIGS. 10-11 are an example of modified 256-QAM using Reflected Pair ofBRGC.

FIGS. 12-13 are an example of modified 1024-QAM using Reflected Pair ofBRGC(0-511).

FIGS. 14-15 are an example of modified 1024-QAM using Reflected Pair ofBRGC(512-1023).

FIGS. 16-17 are an example of modified 4096-QAM using Reflected Pair ofBRGC(0-511).

FIGS. 18-19 are an example of modified 4096-QAM using Reflected Pair ofBRGC(512-1023).

FIGS. 20-21 are an example of modified 4096-QAM using Reflected Pair ofBRGC(1024-1535).

FIGS. 22-23 are an example of modified 4096-QAM using Reflected Pair ofBRGC(1536-2047).

FIGS. 24-25 are an example of modified 4096-QAM using Reflected Pair ofBRGC(2048-2559).

FIGS. 26-27 are an example of modified 4096-QAM using Reflected Pair ofBRGC(2560-307).

FIGS. 28-29 are an example of modified 4096-QAM using Reflected Pair ofBRGC(3072-3583).

FIGS. 30-31 are an example of modified 4096-QAM using Reflected Pair ofBRGC(3584-4095).

FIG. 32 is an example of Bit mapping of Modified-QAM where 256-QAM ismodified using BRGC.

FIG. 33 is an example of transformation of MQAM into Non-uniformconstellation.

FIG. 34 is an example of digital transmission system.

FIG. 35 is an example of an input processor.

FIG. 36 is an information that can be included in Base band (BB).

FIG. 37 is an example of BICM.

FIG. 38 is an example of shortened/punctured encoder.

FIG. 39 is an example of applying various constellations.

FIG. 40 is another example of cases where compatibility betweenconventional systems is considered.

FIG. 41 is a frame structure which comprises preamble for L1 signalingand data symbol for PLP data.

FIG. 42 is an example of frame builder.

FIG. 43 is an example of pilot insert (404) shown in FIG. 4.

FIG. 44 is a structure of SP.

FIG. 45 is a new SP structure or Pilot Pattern (PP) 5.

FIG. 46 is a suggested PP5′ structure.

FIG. 47 is a relationship between data symbol and preamble.

FIG. 48 is another relationship between data symbol and preamble.

FIG. 49 is an example of cable channel delay profile.

FIG. 50 is scattered pilot structure that uses z=56 and z=112.

FIG. 51 is an example of modulator based on OFDM.

FIG. 52 is an example of preamble structure.

FIG. 53 is an example of Preamble decoding.

FIG. 54 is a process for designing more optimized preamble.

FIG. 55 is another example of preamble structure

FIG. 56 is another example of Preamble decoding.

FIG. 57 is an example of Preamble structure.

FIG. 58 is an example of L1 decoding.

FIG. 59 is an example of analog processor.

FIG. 60 is an example of digital receiver system.

FIG. 61 is an example of analog processor used at receiver.

FIG. 62 is an example of demodulator.

FIG. 63 is an example of frame parser.

FIG. 64 is an example of BICM demodulator.

FIG. 65 is an example of LDPC decoding using shortening/puncturing.

FIG. 66 is an example of output processor.

FIG. 67 is an example of L1 block repetition rate of 8 MHz.

FIG. 68 is an example of L1 block repetition rate of 8 MHz.

FIG. 69 is a new L1 block repetition rate of 7.61 MHz.

FIG. 70 is an example of L1 signaling which is transmitted in frameheader.

FIG. 71 is preamble and L1 Structure simulation result.

FIG. 72 is an example of symbol interleaver.

FIG. 73 is an example of an L1 block transmission.

FIG. 74 is another example of L1 signaling transmitted within a frameheader.

FIG. 75 is an example of frequency or time interleaving/deinterleaving.

FIG. 76 is a table analyzing overhead of L1 signaling which istransmitted in FECFRAME header at ModCod Header Insert (307) on datapath of BICM module shown in FIG. 3.

FIG. 77 is showing a structure for FECFRAME header for minimizingoverhead.

FIG. 78 is showing a bit error rate (BER) performance of theaforementioned L1 protection.

FIG. 79 is showing examples of a transmission frame and FEC framestructure.

FIG. 80 is showing an example of L1 signaling.

FIG. 81 is showing an example of L1-pre signaling.

FIG. 82 is showing a structure of L1 signaling block.

FIG. 83 is showing an L1 time interleaving.

FIG. 84 is showing an example of extracting modulation and codeinformation.

FIG. 85 is showing another example of L1-pre signaling.

FIG. 86 is showing an example of scheduling of L1 signaling block thatis transmitted in preamble.

FIG. 87 is showing an example of L1-pre signaling where power boostingis considered.

FIG. 88 is showing an example of L1 signaling.

FIG. 89 is showing another example of extracting modulation and codeinformation.

FIG. 90 is showing another example of extracting modulation and codeinformation.

FIG. 91 is showing an example of L1-pre synchronization.

FIG. 92 is showing an example of L1-pre signaling.

FIG. 93 is showing an example of L1 signaling.

FIG. 94 is showing an example of L1 signalling path.

FIG. 95 is another example of L1 signaling transmitted within a frameheader.

FIG. 96 is another example of L1 signaling transmitted within a frameheader.

FIG. 97 is another example of L1 signaling transmitted within a frameheader.

FIG. 98 is showing an example of L1 signaling.

FIG. 99 is an example of symbol interleaver.

FIG. 100 is showing an interleaving performance of time interleaver ofFIG. 99.

FIG. 101 is an example of symbol interleaver.

FIG. 102 is showing an interleaving performance of time interleaver ofFIG. 101.

FIG. 103 is an example of symbol deinterleaver.

FIG. 104 is another example of time interleaving.

FIG. 105 is a result of interleaving using method shown in FIG. 104.

FIG. 106 is an example of addressing method of FIG. 105.

FIG. 107 is another example of L1 time interleaving.

FIG. 108 is an example of symbol deinterleaver.

FIG. 109 is another example of deinterleaver.

FIG. 110 is an example of symbol deinterleaver.

FIG. 111 is an example of row and column addresses for timedeinterleaving.

FIG. 112 shows an example of general block interleaving in a data symboldomain where pilots are not used.

FIG. 113 is an example of an OFDM transmitter which uses data slices.

FIG. 114 is an example of an OFDM receiver which uses data slice.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In the following description, the term “service” is indicative of eitherbroadcast contents which can be transmitted/received by the signaltransmission/reception apparatus.

Quadrature amplitude modulation (QAM) using Binary Reflected Gray Code(BRGC) is used as modulation in a broadcasting transmission environmentwhere conventional Bit Interleaved Coded Modulation (BICM) is used. FIG.1 shows an example of 64-QAM used in European DVB-T.

BRGC can be made using the method shown in FIG. 2. An n bit BRGC can bemade by adding a reverse code of (n−1) bit BRGC (i.e., reflected code)to a back of (n−1) bit, by adding 0s to a front of original (n−1) bitBRGC, and by adding is to a front of reflected code. The BRGC code madeby this method has a Hamming distance between adjacent codes of one (1).In addition, when BRGC is applied to QAM, the Hamming distance between apoint and the four points which are most closely adjacent to the point,is one (1) and the Hamming distance between the point and another fourpoints which are second most closely adjacent to the point, is two (2).Such characteristics of Hamming distances between a specificconstellation point and other adjacent points can be dubbed as Graymapping rule in QAM.

To make a system robust against Additive White Gaussian Noise (AWGN),distribution of signals transmitted from a transmitter can be made closeto Gaussian distribution. To be able to do that, locations of points inconstellation can be modified. FIG. 3 shows an output close to Gaussianby modifying 64-QAM used in DVB-T. Such constellation can be dubbed asNon-uniform QAM (NU-QAM).

To make a constellation of Non-uniform QAM, Gaussian CumulativeDistribution Function (CDF) can be used. In case of 64, 256, or 1024QAM, i.e., 2̂N AMs, QAM can be divided into two independent N-PAM. Bydividing Gaussian CDF into N sections of identical probability and byallowing a signal point in each section to represent the section, aconstellation having Gaussian distribution can be made. In other words,coordinate xj of newly defined non-uniform N-PAM can be defined asfollows:

$\begin{matrix}{{{\int_{- \infty}^{x_{j}}{\frac{1}{\sqrt{2\; \pi}}^{- \frac{x^{2}}{2}}\ {x}}} = p_{j}},{p_{j} \in \{ {\frac{1}{2\; N},\frac{3}{2\; N},\ldots \mspace{14mu},\frac{{2\; N} - 1}{2\; N}} \}}} & ( {{Eq}.\mspace{14mu} 1} )\end{matrix}$

FIG. 3 is an example of transforming 64QAM of DVB-T into NU-64QAM usingthe above methods. FIG. 3 represents a result of modifying coordinatesof each axis and Q axis using the above methods and mapping the previousconstellation points to newly defined coordinates. In case of 32, 128,or 512 QAM, i.e., cross QAM, which is not 2̂N QAM, by modifying Pjappropriately, a new coordinate can be found.

One embodiment of the present invention can modify QAM using BRGC byusing characteristics of BRGC. As shown in FIG. 4, the Hamming distancebetween Reflected pair in BRGC is one because it differs only in one bitwhich is added to the front of each code. FIG. 5 shows thecharacteristics in QAM where Reflected pair exists for each I axis and Qaxis. In this figure, Reflected pair exists on each side of the dottedblack line.

By using Reflected pairs existing in QAM, an average power of a QAMconstellation can be lowered while keeping Gray mapping rule in QAM. Inother words, in a constellation where an average power is normalized as1, the minimum Euclidean distance in the constellation can be increased.When this modified QAM is applied to broadcasting or communicationsystems, it is possible to implement either a more noise-robust systemusing the same energy as a conventional system or a system with the sameperformance as a conventional system but which uses less energy.

FIG. 6 shows a method of modifying QAM using Reflected pair of BRGC.FIG. 6 a shows a constellation and FIG. 6 b shows a flowchart formodifying QAM using Reflected pair of BRGC. First, a target point whichhas the highest power among constellation points needs to be found.Candidate points are points where that target point can move and are theclosest neighbor points of the target point s reflected pair. Then, anempty point (i.e., a point which is not yet taken by other points)having the smallest power needs to be found among the candidate pointsand the power of the target point and the power of a candidate point arecompared. If the power of the candidate point is smaller, the targetpoint moves to the candidate point. These processes are repeated untilan average power of the points on constellation reaches a minimum whilekeeping Gray mapping rule.

FIG. 7 shows an example of modified 64/256/1024/4096-QAM. The Graymapped values correspond to FIGS. 8˜31 respectively. In addition tothese examples, other types of modified QAM which enables identicalpower optimization can be realized. This is because a target point canmove to multiple candidate points. The suggested modified QAM can beapplied to, not only the 64/256/1024/4096-QAM, but also cross QAM, abigger size QAM, or modulations using other BRGC other than QAM.

FIG. 32 shows an example of Bit mapping of Modified-QAM where 256-QAM ismodified using BRGC. FIG. 32 a and FIG. 32 b show mapping of MostSignificant Bits (MSB). Points designated as filled circles representmappings of ones and points designated as blank circles representmappings of zeros. In a same manner, each bit is mapped as shown infigures from (a) through (h) in FIG. 32, until Least SignificantBits(LSB) are mapped. As shown in FIG. 32, Modified-QAM can enable bitdecision using only I or Q axes as conventional QAM, except for a bitwhich is next to MSB (FIG. 32 c and FIG. 32 d). By using thesecharacteristics, a simple receiver can be made by partially modifying areceiver for QAM. An efficient receiver can be implemented by checkingboth I and Q values only when determining bit next to MSB and bycalculating only I or Q for the rest of bits. This method can be appliedto Approximate LLR, Exact LLR, or Hard decision.

By using the Modified-QAM or MQAM, which uses the characteristics ofabove BRGC, Non-uniform constellation or NU-MQAM can be made. In theabove equation where Gaussian CDF is used, Pj can be modified to fitMQAM. Just like QAM, in MQAM, two PAMs having I axis and Q axis can beconsidered. However, unlike QAM where a number of points correspondingto a value of each PAM axis are identical, the number of points changesin MQAM. If a number of points that corresponds to jth value of PAM isdefined as nj in a MQAM where a total of M constellation points exist,then Pj can be defined as follows:

$\begin{matrix}{{{\int_{- \infty}^{x_{j}}{\frac{1}{\sqrt{2\; \pi}}^{- \frac{x^{2}}{2}}\ {x}}} = p_{j}}{{p_{j} = \frac{{\sum\limits_{i = 0}^{i = {j - 1}}\; n_{i}} + \frac{n_{j}}{2\; N}}{M}},{n_{0} = 0}}} & ( {{Eq}.\mspace{14mu} 2} )\end{matrix}$

By using the newly defined Pj, MQAM can be transformed into Non-uniformconstellation. Pj can be defiend as follows for the example of 256-MQAM.

$p_{j} \in \{ {\frac{2.5}{256},\frac{10}{256},\frac{22}{256},\frac{36}{256},\frac{51}{256},\frac{67}{256},\frac{84}{256},\frac{102}{256},\frac{119.5}{256},\frac{136.5}{256},\frac{154}{256},\frac{172}{256},\frac{189}{256},\frac{205}{256},\frac{220}{256},\frac{234}{256},\frac{246}{256},\frac{253.5}{256}} \}$

FIG. 33 is an example of transformation of MQAM into Non-uniformconstellation. The NU-MQAM made using these methods can retaincharacteristics of MQAM receivers with modified coordinates of each PAM.Thus, an efficient receiver can be implemented. In addition, a morenoise-robust system than the previous NU-QAM can be implemented. For amore efficient broadcasting transmission system, hybridizing MQAM andNU-MQAM is possible. In other words, a more noise-robust system can beimplemented by using MQAM for an environment where an error correctioncode with high code rate is used and by using NU-MQAM otherwise. Forsuch a case, a transmitter can let a receiver have information of coderate of an error correction code currently used and a kind of modulationcurrently used such that the receiver can demodulate according to themodulation currently used.

FIG. 34 shows an example of digital transmission system. Inputs cancomprise a number of MPEG-TS streams or GSE (General StreamEncapsulation) streams. An input processor module 101 can addtransmission parameters to input stream and perform scheduling for aBICM module 102. The BICM module 102 can add redundancy and interleavedata for transmission channel error correction. A frame builder 103 canbuild frames by adding physical layer signaling information and pilots.A modulator 104 can perform modulation on input symbols in efficientmethods. An analog processor 105 can perform various processes forconverting input digital signals into output analog signals.

FIG. 35 shows an example of an input processor. Input MPEG-TS or GSEstream can be transformed by input preprocessor into a total of nstreams which will be independently processed. Each of those streams canbe either a complete TS frame which includes multiple service componentsor a minimum TS frame which includes service component (i.e., video oraudio). In addition, each of those streams can be a GSE stream whichtransmits either multiple services or a single service.

Input interface module 202-1 can allocate a number of input bits equalto the maximum data field capacity of a Baseband (BB) frame. A paddingmay be inserted to complete the LDPC/BCH code block capacity. The inputstream sync module 203-1 can provide a mechanism to regenerate, in thereceiver, the clock of the Transport Stream (or packetized GenericStream), in order to guarantee end-to-end constant bit rates and delay.

In order to allow the Transport Stream recombining without requiringadditional memory in the receiver, the input Transport Streams aredelayed by delay compensators 204-1˜n considering interleavingparameters of the data PLPs in a group and the corresponding common PLP.Null packet deleting modules 205-1˜n can increase transmissionefficiency by removing inserted null packet for a case of VBR (variablebit rate) service. Cyclic Redundancy Check (CRC) encoder modules 206-1˜ncan add CRC parity to increase transmission reliability of BB frame. BBheader inserting modules 207-1˜n can add BB frame header at a beginningportion of BB frame. Information that can be included in BB header isshown in FIG. 36.

A Merger/slicer module 208 can perform BB frame slicing from each PLP,merging BB frames from multiple PLPs, and scheduling each BB framewithin a transmission frame. Therefore, the merger/slicer module 208 canoutput L1 signaling information which relates to allocation of PLP inframe. Lastly, a BB scrambler module 209 can randomize input bitstreamsto minimize correlation between bits within bitstreams. The modules inshadow in FIG. 35 are modules used when transmission system uses asingle PLP, the other modules in FIG. 35 are modules used when thetransmission device uses multiple PLPs.

FIG. 37 shows an example of BICM module. FIG. 37 a shows data path andFIG. 37 b shows L1 path of BICM module. An outer coder module 301 and aninner coder module 303 can add redundancy to input bitstreams for errorcorrection. An outer interleaver module 302 and an inner interleavermodule 304 can interleave bits to prevent burst error. The Outerinterleaver module 302 can be omitted if the BICM is specifically forDVB-C2. A bit demux module 305 can control reliability of each bitoutput from the inner interleaver module 304. A symbol mapper module 306can map input bitstreams into symbol streams. At this time, it ispossible to use any of a conventional QAM, an MQAM which uses theaforementioned BRGC for performance improvement, an NU-QAM which usesNon-uniform modulation, or an NU-MQAM which uses Non-uniform modulationapplied BRGC for performance improvement. To construct a system which ismore robust against noise, combinations of modulations using MQAM and/orNU-MQAM depending on the code rate of the error correction code and theconstellation capacity can be considered. At this time, the Symbolmapper module 306 can use a proper constellation according to the coderate and constellation capacity. FIG. 39 shows an example of suchcombinations.

Case 1 shows an example of using only NU-MQAM at low code rate forsimplified system implementation. Case 2 shows an example of usingoptimized constellation at each code rate. The transmitter can sendinformation about the code rate of the error correction code and theconstellation capacity to the receiver such that the receiver can use anappropriate constellation. FIG. 40 shows another example of cases wherecompatibility between conventional systems is considered. In addition tothe examples, further combinations for optimizing the system arepossible.

The ModCod Header inserting module 307 shown in FIG. 37 can takeAdaptive coding and modulation (ACM)/Variable coding and modulation(VCM) feedback information and add parameter information used in codingand modulation to a FEC block as header. The Modulation type/Coderate(ModCod) header can include the following information:

-   -   FEC type (1 bits) long or short LDPC    -   Coderate (3 bits)    -   Modulation (3 bits) up-to 64K QAM    -   PLP identifier (8 bits)

The Symbol interleaver module 308 can perform interleaving in symboldomain to obtain additional interleaving effects. Similar processesperformed on data path can be performed on L1 signaling path but withpossibly different parameters (301-1˜308-1). At this point, ashortened/punctured code module (303-1) can be used for inner code.

FIG. 38 shows an example of LDPC encoding using shortening/puncturing.Shortening process can be performed on input blocks which have less bitsthan a required number of bits for LDPC encoding as many zero bitsrequired for LDPC encoding can be padded (301 c). Zero Padded inputbitstreams can have parity bits through LDPC encoding (302 c). At thistime, for bitstreams that correspond to original bitstreams, zeros canbe removed (303 c) and for parity bitstreams, puncturing (304 c) can beperformed according to code-rates. These processed informationbitstreams and parity bitstreams can be multiplexed into originalsequences and outputted (305 c).

FIG. 41 shows a frame structure which comprises preamble for L1signaling and data symbol for PLP data. It can be seen that preamble anddata symbols are cyclically generated, using one frame as a unit. Datasymbols comprise PLP type 0 which is transmitted using a fixedmodulation/coding and PLP type 1 which is transmitted using a variablemodulation/coding. For PLP type 0, information such as modulation, FECtype, and FEC code rate are transmitted in preamble (see FIG. 42 Frameheader insert 401). For PLP type 1, corresponding information can betransmitted in FEC block header of a data symbol (see FIG. 37 ModCodheader insert 307). By the separation of PLP types, ModCod overhead canbe reduced by 3-4% from a total transmission rate, for PLP type0 whichis transmitted at a fixed bit rate. At a receiver, for fixedmodulation/coding PLP of PLP type 0, Frame header remover r401 shown inFIG. 63 can extract information on Modulation and FEC code rate andprovide the extracted information to a BICM decoding module. Forvariable modulation/coding PLP of PLP type 1, ModCod extracting modules,r307 and r307-1 shown in FIG. 64 can extract and provide the parametersnecessary for BICM decoding.

FIG. 42 shows an example of a frame builder. A frame header insertingmodule 401 can form a frame from input symbol streams and can add frameheader at front of each transmitted frame. The frame header can includethe following information:

-   -   Number of bonded channels (4 bits)    -   Guard interval (2 bits)    -   PAPR (2 bits)    -   Pilot pattern (2 bits)    -   Digital System identification (16 bits)    -   Frame identification (16 bits)    -   Frame length (16 bits) number of Orthogonal Frequency Division        Multiplexing (OFDM) symbols per frame    -   Superframe length (16 bits) number of frames per superframe    -   number of PLPs (8 bits)    -   for each PLP

PLP identification (8 bits)

Channel bonding id (4 bits)

PLP start (9 bits)

PLP type (2 bits) common PLP or others

PLP payload type (5 bits)

MC type (1 bit) -fixed/variable modulation & coding

if MC type==fixed modulation & coding

FEC type (1 bits) -long or short LDPC

Coderate (3 bits)

Modulation (3 bits) -up-to 64K QAM

end if;

Number of notch channels (2 bits)

for each notch

Notch start (9 bits)

Notch width (9 bits)

end for;

PLP width (9 bits) -max number of FEC blocks of PLP

PLP time interleaving type (2 bits)

end for;

-   -   CRC-32 (32 bits)

Channel bonding environment is assumed for L1 information transmitted inFrame header and data that correspond to each data slice is defined asPLP. Therefore, information such as PLP identifier, channel bondingidentifier, and PLP start address are required for each channel used inbonding. One embodiment of this invention suggests transmitting ModCodfield in FEC frame header if PLP type supports variablemodulation/coding and transmitting ModCod field in Frame header if PLPtype supports fixed modulation/coding to reduce signaling overhead. Inaddition, if a Notch band exists for each PLP, by transmitting the startaddress of the Notch and its width, decoding corresponding carriers atthe receiver can become unnecessary.

FIG. 43 shows an example of Pilot Pattern 5 (PP5) applied in a channelbonding environment. As shown, if SP positions are coincident withpreamble pilot positions, irregular pilot structure can occur.

FIG. 43 a shows an example of pilot inserting module 404 as shown inFIG. 42. As represented in FIG. 43, if a single frequency band (forexample, 8 MHz) is used, the available bandwidth is 7.61 MHz, but ifmultiple frequency bands are bonded, guard bands can be removed, thus,frequency efficiency can increase greatly. FIG. 43 b is an example ofpreamble inserting module 504 as shown in FIG. 51 that is transmitted atthe front part of the frame and even with channel bonding, the preamblehas repetition rate of 7.61 MHz, which is bandwidth of L1 block. This isa structure considering the bandwidth of a tuner which performs initialchannel scanning.

Pilot Patterns exist for both Preamble and Data Symbols. For datasymbol, scattered pilot (SP) patterns can be used. Pilot Pattern 5 (PP5)and Pilot Pattern 7 (PP7) of T2 can be good candidates forfrequency-only interpolation. PP5 has x=12, y=4, z=48 for GI= 1/64 andPP7 has x=24, y=4, z=96 for GI= 1/128. Additional time-interpolation isalso possible for a better channel estimation. Pilot patterns forpreamble can cover all possible pilot positions for initial channelacquisition. In addition, preamble pilot positions should be coincidentwith SP positions and a single pilot pattern for both the preamble andthe SP is desired. Preamble pilots could also be used fortime-interpolation and every preamble could have an identical pilotpattern. These requirements are important for C2 detection in scanningand necessary for frequency offset estimation with scrambling sequencecorrelation. In a channel bonding environment, the coincidence in pilotpositions should also be kept for channel bonding because irregularpilot structure may degrade interpolation performance.

In detail, if a distance z between scattered pilots (SPs) in an OFDMsymbol is 48 and if a distance y between SPs corresponding to a specificSP carrier along the time axis is 4, an effective distance x after timeinterpolation becomes 12. This is when a guard interval (GI) fraction is1/64. If GI fraction is 1/128, x=24, y=4, and z=96 can be used. Ifchannel bonding is used, SP positions can be made coincident withpreamble pilot positions by generating non-continuous points inscattered pilot structure.

At this time, preamble pilot positions can be coincident with every SPpositions of data symbol. When channel bonding is used, data slice wherea service is transmitted, can be determined regardless of 8 MHzbandwidth granularity. However, for reducing overhead for data sliceaddressing, transmission starting from SP position and ending at SPposition can be chosen.

When a receiver receives such SPs, if necessary, channel estimationmodule r501 shown in FIG. 62 can perform time interpolation to obtainpilots shown in dotted lines in FIG. 43 and perform frequencyinterpolation. At this time, for non-continuous points of whichintervals are designated as 32 in FIG. 43, either performinginterpolations on left and right separately or performing interpolationson only one side then performing interpolation on the other side byusing the already interpolated pilot positions of which interval is 12as a reference point can be implemented. At this time, data slice widthcan vary within 7.61 MHz, thus, a receiver can minimize powerconsumption by performing channel estimation and decoding only necessarysubcarriers.

FIG. 44 shows another example of PP5 applied in channel bondingenvironment or a structure of SP for maintaining effective distance x as12 to avoid irregular SP structure shown in FIG. 43 when channel bondingis used. FIG. 44 a is a structure of SP for data symbol and FIG. 44 b isa structure of SP for preamble symbol.

As shown, if SP distance is kept consistent in case of channel bonding,there will be no problem in frequency interpolation but pilot positionsbetween data symbol and preamble may not be coincident. In other words,this structure does not require additional channel estimation for anirregular SP structure, however, SP positions used in channel bondingand preamble pilot positions become different for each channel.

FIG. 45 shows a new SP structure or PP5 to provide a solution to the twoproblems aforementioned in channel bonding environment. Specifically, apilot distance of x=16 can solve those problems. To preserve pilotdensity or to maintain the same overhead, a PP5′ can have x=16, y=3,z=48 for GI= 1/64 and a PP7′ can have x=16, y=6, z=96 for GI= 1/128.Frequency-only interpolation capability can still be maintained. Pilotpositions are depicted in FIG. 45 for comparison with PP5 structure.

FIG. 46 shows an example of a new SP Pattern or PPS structure in channelbonding environment. As shown in FIG. 46, whether either single channelor channel bonding is used, an effective pilot distance x=16 can beprovided. In addition, because SP positions can be made coincident withpreamble pilot positions, channel estimation deterioration caused by SPirregularity or non-coincident SP positions can be avoided. In otherwords, no irregular SP position exists for freq-interpolator andcoincidence between preamble and SP positions is provided.

Consequently, the proposed new SP patterns can be advantageous in thatsingle SP pattern can be used for both single and bonded channel; noirregular pilot structure can be caused, thus a good channel estimationis possible; both preamble and SP pilot positions can be keptcoincident; pilot density can be kept the same as for PP5 and PP7respectively; and Frequency-only interpolation capability can also bepreserved.

In addition, the preamble structure can meet the requirements such aspreamble pilot positions should cover all possible SP positions forinitial channel acquisition; maximum number of carriers should be 3409(7.61 MHz) for initial scanning; exactly same pilot patterns andscrambling sequence should be used for C2 detection; and nodetection-specific preamble like P1 in T2 is required.

In terms of relation with frame structure, data slice positiongranularity may be modified to 16 carriers rather than 12, thus, lessposition addressing overhead can occur and no other problem regardingdata slice condition, Null slot condition etc can be expected.

Therefore, at channel estimation module r501 of FIG. 62, pilots in everypreamble can be used when time interpolation of SP of data symbol isperformed. Therefore, channel acquisition and channel estimation at theframe boundaries can be improved.

Now, regarding requirements related to the preamble and the pilotstructure, there is consensus in that positions of preamble pilots andSPs should coincide regardless of channel bonding; the number of totalcarriers in L1 block should be dividable by pilot distance to avoidirregular structure at band edge; L1 blocks should be repeated infrequency domain; and L1 blocks should always be decodable in arbitrarytuner window position. Additional requirements would be that pilotpositions and patterns should be repeated by period of 8 MHz; correctcarrier frequency offset should be estimated without channel bondingknowledge; and L1 decoding (re-ordering) is impossible before thefrequency offset is compensated.

FIG. 47 shows a relationship between data symbol and preamble whenpreamble structures as shown in FIG. 52 and FIG. 53 are used. L1 blockcan be repeated by period of 6 MHz. For L1 decoding, both frequencyoffset and Preamble shift pattern should be found. L1 decoding is notpossible in arbitrary tuner position without channel bonding informationand a receiver cannot differentiate between preamble shift value andfrequency offset.

Thus, a receiver, specifically for Frame header remover r401 shown inFIG. 63 to perform L1 signal decoding, channel bonding structure needsto be obtained. Because preamble shift amount expected at two verticallyshadowed regions in FIG. 47 is known, time/freq synchronizing moduler505 in FIG. 62 can estimate carrier frequency offset. Based on theestimation, L1 signaling path (r308-1˜r301-1) in FIG. 64 can decode L1.

FIG. 48 shows a relationship between data symbol and preamble when thepreamble structure as shown in FIG. 55 is used. L1 block can be repeatedby period of 8 MHz. For L1 decoding, only frequency offset needs to befound and channel bonding knowledge may not be required. Frequencyoffset can be easily estimated by using known Pseudo Random BinarySequence (PRBS) sequence. As shown in FIG. 48, preamble and data symbolsare aligned, thus, additional sync search can become un-necessary.Therefore, for a receiver, specifically for the Frame header removermodule r401 shown in FIG. 63, it is possible that only correlation peakwith pilot scrambling sequence needs to be obtained to perform L1 signaldecoding. The time/freq synchronizing module r505 in FIG. 62 canestimate carrier frequency offset from peak position.

FIG. 49 shows an example of cable channel delay profile.

From the point of view of pilot design, current GI already over-protectsdelay spread of cable channel. In the worst case, redesigning thechannel model can be an option. To repeat the pattern exactly every 8MHz, the pilot distance should be a divisor of 3584 carriers (z=32 or56). A pilot density of z=32 can increase pilot overhead, thus, z=56 canbe chosen. Slightly less delay coverage may not be an important in cablechannel. For example, it can be 8 μs for PP5′ and 4 μs for PP7′ comparedto 9.3 μs (PP5) and 4.7 μs (PP7). Meaningful delays can be covered byboth pilot patterns even in a worst case. For preamble pilot position,no more than all SP positions in data symbol are necessary.

If the −40 dB delay path can be ignored, actual delay spread can become2.5 us, 1/64 GI=7 s, or 1/128 GI=3.5 μs. This shows that pilot distanceparameter, z=56 can be a good enough value. In addition, z=56 can be aconvenient value for structuring pilot pattern that enables preamblestructure shown in FIG. 48.

FIG. 50 shows scattered pilot structure that uses z=56 and z=112 whichis constructed at pilot inserting module 404 in FIG. 42. PP5′ (x=14,y=4, z=56) and PP7′ (x=28, y=4, z=112) are proposed. Edge carriers couldbe inserted for closing edge.

As shown in FIG. 50, pilots are aligned at 8 MHz from each edge of theband, every pilot position and pilot structure can be repeated every 8MHz. Thus, this structure can support the preamble structure shown inFIG. 48. In addition, a common pilot structure between preamble and datasymbols can be used. Therefore, channel estimation module r501 in FIG.62 can perform channel estimation using interpolation on preamble anddata symbols because no irregular pilot pattern can occur, regardless ofwindow position which is decided by data slice locations. At this time,using only frequency interpolation can be enough to compensate channeldistortion from delay spread. If time interpolation is performedadditionally, more accurate channel estimation can be performed.

Consequently, in the new proposed pilot pattern, pilot position andpattern can be repeated based on a period of 8 MHz. A single pilotpattern can be used for both preamble and data symbols. L1 decoding canalways be possible without channel bonding knowledge. In addition, theproposed pilot pattern may not affect commonality with T2 because thesame pilot strategy of scattered pilot pattern can be used; T2 alreadyuses 8 different pilot patterns; and no significant receiver complexitycan be increased by modified pilot patterns. For a pilot scramblingsequence, the period of PRBS can be 2047 (m-sequence); PRBS generationcan be reset every 8 MHz, of which the period is 3584; pilot repetitionrate of 56 can be also co-prime with 2047; and no PAPR issue can beexpected.

FIG. 51 shows an example of a modulator based on OFDM. Input symbolstreams can be transformed into time domain by IFFT module 501. Ifnecessary, peak-to-average power ratio (PAPR) can be reduced at PAPRreducing module 502. For PAPR methods, Active constellation extension(ACE) or tone reservation can be used. GI inserting module 503 can copya last part of effective OFDM symbol to fill guard interval in a form ofcyclic prefix.

Preamble inserting module 504 can insert preamble at the front of eachtransmitted frame such that a receiver can detect digital signal, frameand acquire time/freq offset acquisition. At this time, the preamblesignal can perform physical layer signaling such as FFT size (3 bits)and Guard interval size (3 bits). The Preamble inserting module 504 canbe omitted if the modulator is specifically for DVB-C2.

FIG. 52 shows an example of a preamble structure for channel bonding,generated at preamble inserting module 504 in FIG. 51. One complete L1block should be “always decodable” in any arbitrary 7.61 MHz tuningwindow position and no loss of L1 signaling regardless of tuner windowposition should occur. As shown, L1 blocks can be repeated in frequencydomain by period of 6 MHz. Data symbol can be channel bonded for every 8MHz. If, for L1 decoding, a receiver uses a tuner such as the tuner r603represented in FIG. 61 which uses a bandwidth of 7.61 MHz, the Frameheader remover r401 in FIG. 63 needs to rearrange the received cyclicshifted L1 block (FIG. 53) to its original form. This rearrangement ispossible because L1 block is repeated for every 6 MHz block. FIG. 53 acan be reordered into FIG. 53 b.

FIG. 54 shows a process for designing a more optimized preamble. Thepreamble structure of FIG. 52 uses only 6 MHz of total tuner bandwidth7.61 MHz for L1 decoding. In terms of spectrum efficiency, tunerbandwidth of 7.61 MHz is not fully utilized. Therefore, there can befurther optimization in spectrum efficiency.

FIG. 55 shows another example of preamble structure or preamble symbolsstructure for full spectrum efficiency, generated at Frame HeaderInserting module 401 in FIG. 42. Just like data symbol, L1 blocks can berepeated in frequency domain by period of 8 MHz. One complete L1 blockis still “always decodable” in any arbitrary 7.61 MHz tuning windowposition. After tuning, the 7.61 MHz data can be regarded as a virtuallypunctured code. Having exactly the same bandwidth for both the preambleand data symbols and exactly the same pilot structure for both thepreamble and data symbols can maximize spectrum efficiency. Otherfeatures such as cyclic shifted property and not sending L1 block incase of no data slice can be kept unchanged. In other words, thebandwidth of preamble symbols can be identical with the bandwidth ofdata symbols or, as shown in FIG. 57, the bandwidth of the preamblesymbols can be the bandwidth of the tuner (here, it's 7.61 MHz). Thetuner bandwidth can be defined as a bandwidth that corresponds to anumber of total active carriers when a single channel is used. That is,the bandwidth of the preamble symbol can correspond to the number oftotal active carriers (here, it's 7.61 MHz).

FIG. 56 shows a virtually punctured code. The 7.61 MHz data among the 8MHz L1 block can be considered as punctured coded. When a tuner r603shown in FIG. 61 uses 7.61 MHz bandwidth for L1 decoding, Frame headerremover r401 in FIG. 63 needs to rearrange received, cyclic shifted L1block into original form as shown in FIG. 56. At this time, L1 decodingis performed using the entire bandwidth of the tuner. Once the L1 blockis rearranged, a spectrum of the rearranged L1 block can have a blankregion within the spectrum as shown in upper right side of FIG. 56because an original size of L1 block is 8 MHz bandwidth.

Once the blank region is zero padded, either after deinterleaving insymbol domain by the freq. deinterleaver r403 in FIG. 63 or by thesymbol deinterleaver r308-1 in FIG. 64 or after deinterleaving in bitdomain by the symbol demapper r306-1, bit mux r305-1, and innerdeinterleaver r304-1 in FIG. 64, the block can have a form which appearsto be punctured as shown in lower right side of FIG. 56.

This L1 block can be decoded at the punctured/shortened decode moduler303-1 in FIG. 64. By using these preamble structure, the entire tunerbandwidth can be utilized, thus spectrum efficiency and coding gain canbe increased. In addition, an identical bandwidth and pilot structurecan be used for the preamble and data symbols.

In addition, if the preamble bandwidth or the preamble symbols bandwidthis set as a tuner bandwidth as shown in FIG. 58, (it's 7.61 MHz in theexample), a complete L1 block can be obtained after rearrangement evenwithout puncturing. In other words, for a frame having preamble symbols,wherein the preamble symbols have at least one layer 1 (L1) block, itcan be said, the L1 block has 3408 active subcarriers and the 3408active subcarriers correspond to 7.61 MHz of 8 MHz Radio Frequency (RF)band.

Thus, spectrum efficiency and L1 decoding performance can be maximized.In other words, at a receiver, decoding can be performed atpunctured/shortened decode module r303-1 in FIG. 64, after performingonly deinterleaving in the symbol domain.

Consequently, the proposed new preamble structure can be advantageous inthat it s fully compatible with previously used preamble except that thebandwidth is different; L1 blocks are repeated by period of 8 MHz; L1block can be always decodable regardless of tuner window position; Fulltuner bandwidth can be used for L1 decoding; maximum spectrum efficiencycan guarantee more coding gain; incomplete L1 block can be considered aspunctured coded; simple and same pilot structure can be used for bothpreamble and data; and identical bandwidth can be used for both preambleand data.

FIG. 59 shows an example of an analog processor. A DAC module 601 canconvert digital signal input into analog signal. After transmissionfrequency bandwidth is up-converted (602) and analog filtered (603)signal can be transmitted.

FIG. 60 shows an example of a digital receiver system. Received signalis converted into digital signal at an analog process module r105. Ademodulator r104 can convert the signal into data in frequency domain. Aframe parser r103 can remove pilots and headers and enable selection ofservice information that needs to be decoded. A BICM demodulator r102can correct errors in the transmission channel. An output processor r101can restore the originally transmitted service stream and timinginformation.

FIG. 61 shows an example of analog processor used at the receiver. ATuner/AGC module r603 can select desired frequency bandwidth fromreceived signal. A down converting module r602 can restore baseband. AnADC module r601 can convert analog signal into digital signal.

FIG. 62 shows an example of demodulator. A frame detecting module r506can detect the preamble, check if a corresponding digital signal exists,and detect a start of a frame. A time/freq synchronizing module r505 canperform synchronization in time and frequency domains. At this time, fortime domain synchronization, a guard interval correlation can be used.For frequency domain synchronization, correlation can be used or offsetcan be estimated from phase information of a subcarrier that istransmitted in the frequency domain. A preamble removing module r504 canremove preamble from the front of detected frame. A GI removing moduler503 can remove guard interval. A FFT module r501 can transform signalin the time domain into signal in the frequency domain. A channelestimation/equalization module r501 can compensate errors by estimatingdistortion in transmission channel using pilot symbol. The Preambleremoving module r504 can be omitted if the demodulator is specificallyfor DVB-C2.

FIG. 63 shows an example of frame parser. A pilot removing module r404can remove pilot symbol. A freq deinterleaving module r403 can performdeinterleaving in the frequency domain. An OFDM symbol merger r402 canrestore data frame from symbol streams transmitted in OFDM symbols. Aframe header removing module r401 can extract physical layer signalingfrom header of each transmitted frame and remove header. Extractedinformation can be used as parameters for following processes in thereceiver.

FIG. 64 shows an example of a BICM demodulator. FIG. 64 a shows a datapath and FIG. 64 b shows a L1 signaling path. A symbol deinterleaverr308 can perform deinterleaving in the symbol domain. A ModCod extractr307 can extract ModCod parameters from front of each BB frame and makethe parameters available for following adaptive/variable demodulationand decoding processes. A Symbol demapper r306 can demap input symbolstreams into bit Log-Likelyhood Ratio (LLR) streams. The Output bit LLRstreams can be calculated by using a constellation used in a Symbolmapper 306 of the transmitter as reference point. At this point, whenthe aforementioned MQAM or NU-MQAM is used, by calculating both I axisand Q axis when calculating bit nearest from MSB and by calculatingeither I axis or Q axis when calculating the rest bits, an efficientsymbol demapper can be implemented. This method can be applied to, forexample, Approximate LLR, Exact LLR, or Hard decision.

When an optimized constellation according to constellation capacity andcode rate of error correction code at the Symbol mapper 306 of thetransmitter is used, the Symbol demapper r306 of the receiver can obtaina constellation using the code rate and constellation capacityinformation transmitted from the transmitter. The bit mux r305 of thereceiver can perform an inverse function of the bit demux 305 of thetransmitter. The Inner deinterleaver r304 and outer deinterleaver r302of the receiver can perform inverse functions of the inner interleaver304 and outer interleaver 302 of the transmitter, respectively to getthe bitstream in its original sequence. The outer deinterleaver r302 canbe omitted if the BICM demodulator is specifically for DVB-C2.

The inner decoder r303 and outer decoder r301 of the receiver canperform corresponding decoding processes to the inner coder 303 andouter code 301 of the transmitter, respectively, to correct errors inthe transmission channel. Similar processes performed on data path canbe performed on L1 signaling path, but with different parameters(r308-1˜r301-1). At this point, as explained in the preamble part, ashortened/punctured code module r303-1 can be used for L1 signaldecoding.

FIG. 65 shows an example of LDPC decoding using shortening/puncturing. Ademux r301 a can separately output information part and parity part ofsystematic code from input bit streams. For the information part, a zeropadding (r302 a) can be performed according to a number of input bitstreams of LDPC decoder, for the parity part, input bit streams for(r303 a) the LDPC decoder can be generated by depuncturing puncturedpart. LDPC decoding (r304 a) can be performed on generated bit streams,zeros in information part can be removed and output (r305 a).

FIG. 66 shows an example of output processor. A BB descrambler r209 canrestore scrambled (209) bit streams at the transmitter. A Splitter r208can restore BB frames that correspond to multiple PLP that aremultiplexed and transmitted from the transmitter according to PLP path.For each PLP path, a BB header remover r207-1˜n can remove the headerthat is transmitted at the front of the BB frame. A CRC decoder r206-1˜ncan perform CRC decoding and make reliable BB frames available forselection. A Null packet inserting modules r205-1˜n can restore nullpackets which were removed for higher transmission efficiency in theiroriginal location. A Delay recovering modules r204-1˜n can restore adelay that exists between each PLP path.

An output clock recovering modules r203-1˜n can restore the originaltiming of the service stream from timing information transmitted fromthe input stream synchronization modules 203-1˜n. An output interfacemodules r202-1˜n can restore data in TS/GS packet from input bit streamsthat are sliced in BB frame. An output postprocess modules r201-1˜n canrestore multiple TS/GS streams into a complete TS/GS stream, ifnecessary. The shaded blocks shown in FIG. 66 represent modules that canbe used when a single PLP is processed at a time and the rest of theblocks represent modules that can be used when multiple PLPs areprocessed at the same time.

Preamble pilot patterns were carefully designed to avoid PAPR increase,thus, whether L1 repetition rate may increase PAPR needs to beconsidered. The number of L1 information bits varies dynamicallyaccording to the channel bonding, the number of PLPs, etc. In detail, itis necessary to consider things such as fixed L1 block size mayintroduce unnecessary overhead; L1 signaling should be protected morestrongly than data symbols; and time interleaving of L1 block canimprove robustness over channel impairment such as impulsive noise need.

For a L1 block repetition rate of 8 MHz, as shown in FIG. 67, fullspectrum efficiency (26.8% BW increase) is exhibited with virtualpuncturing but the PAPR may be increased since L1 bandwidth is the sameas that of the data symbols. For the repetition rate of 8 MHz, 4K-FFTDVB-T2 frequency interleaving can be used for commonality and the samepattern can repeat itself at a 8 MHz period after interleaving.

For a L1 block repetition rate of 6 MHz, as shown in FIG. 68, reducedspectrum efficiency can be exhibited with no virtual puncturing. Asimilar problem of PAPR as for the 8 MHz case can occur since the L1 anddata symbol bandwidths share LCM=24 MHz. For the repetition rate of 6MHz, 4K-FFT DVB-T2 frequency interleaving can be used for commonalityand the same pattern can repeat itself at a period of 24 MHz afterinterleaving.

FIG. 69 shows a new L1 block repetition rate of 7.61 MHz or full tunerbandwidth. A full spectrum efficiency (26.8% BW increase) can beobtained with no virtual puncturing. There can be no PAPR issue since L1and data symbol bandwidths share LCM≈704 MHz. For the repetition rate of7.61 MHz, 4K-FFT DVB-T2 frequency interleaving can be used forcommonality and the same pattern can repeat itself by period of about1704 MHz after interleaving.

FIG. 70 is an example of L1 signaling which is transmitted in the frameheader. Each information in L1 signaling can be transmitted to thereceiver and can be used as a decoding parameter. Especially, theinformation can be used in L1 signal path shown in FIG. 64 and PLPs canbe transmitted in each data slice. An increased robustness for each PLPcan be obtained.

FIG. 72 is an example of a symbol interleaver 308-1 as shown in L1signaling path in FIG. 37 and also can be an example of itscorresponding symbol deinterleaver r308-1 as shown in L1 signaling pathin FIG. 64. Blocks with tilted lines represent L1 blocks and solidblocks represent data carriers. L1 blocks can be transmitted not onlywithin a single preamble, but also can be transmitted within multipleOFDM blocks. Depending on a size of L1 block, the size of theinterleaving block can vary. In other words, num_L1_sym and L1 span canbe different from each other. To minimize unnecessary overhead, data canbe transmitted within the rest of the carriers of the OFDM symbols wherethe L1 block is transmitted. At this point, full spectrum efficiency canbe guaranteed because the repeating cycle of L1 block is still a fulltuner bandwidth. In FIG. 72, the numbers in blocks with tilted linesrepresent the bit order within a single LDPC block.

Consequently, when bits are written in an interleaving memory in the rowdirection according to a symbol index as shown in FIG. 72 and read inthe column direction according to a carrier index, a block interleavingeffect can be obtained. In other words, one LDPC block can beinterleaved in the time domain and the frequency domain and then can betransmitted. Num_L1_sym can be a predetermined value, for example, anumber between 2˜4 can be set as a number of OFDM symbols. At thispoint, to increase the granularity of the L1 block size, apunctured/shortened LDPC code having a minimum length of the codewordcan be used for L1 protection.

FIG. 73 is an example of an L1 block transmission. FIG. 73 illustratesFIG. 72 in frame domain. As shown on FIG. 73 a, L1 blocks can bespanning in full tuner bandwidth or as shown on FIG. 73 b, L1 blocks canbe partially spanned and the rest of the carriers can be used for datacarrier. In either case, it can be seen that the repetition rate of L1block can be identical to a full tuner bandwidth. In addition, for OFDMsymbols which uses L1 signaling including preamble, only symbolinterleaving can be performed while not allowing data transmission inthat OFDM symbols. Consequently, for OFDM symbol used for L1 signaling,a receiver can decode L1 by performing deinterleaving without datadecoding. At this point, the L1 block can transmit L1 signaling ofcurrent frame or L1 signaling of a subsequent frame. At the receiverside, L1 parameters decoded from L1 signaling decoding path shown inFIG. 64 can be used for decoding process for data path from frame parserof subsequent frame.

In summary, at a transmitter, interleaving blocks of L1 region can beperformed by writing blocks to a memory in a row direction and readingthe written blocks from the memory in a column direction. At a receiver,deinterleaving blocks of L1 region can be performed by writing blocks toa memory in a column direction and reading the written blocks from thememory in a row direction. The reading and writing directions oftransmitter and receiver can be interchanged.

When simulation is performed with assumptions such as CR=½ for L1protection and for T2 commonality; 16-QAM symbol mapping; pilot densityof 6 in the Preamble; number of short LDPC implies required amount ofpuncturing/shortening are made, results or conclusions such as onlypreamble for L1 transmission may not be sufficient; the number of OFDMsymbols depends on the amount of L1 block size; shortest LDPC codeword(e.g. 192 bits information) among shortened/punctured code may be usedfor flexibility and fine granularity; and Padding may be added ifrequired with negligible overhead, can be obtained. The result issummarized in FIG. 71.

Consequently, for a L1 block repetition rate, full tuner bandwidth withno virtual puncturing can be a good solution and still no PAPR issue canarise with full spectrum efficiency. For L1 signaling, efficientsignaling structure can allow maximum configuration in an environment of8 channels bonding, 32 notches, 256 data slices, and 256 PLPs. For L1block structure, flexible L1 signaling can be implemented according toL1 block size. Time interleaving can be performed for better robustnessfor T2 commonality. Less overhead can allow data transmission inpreamble.

Block interleaving of L1 block can be performed for better robustness.The interleaving can be performed with fixed pre-defined number of L1symbols (num_L1_sym) and a number of carriers spanned by L1 as aparameter (L1_span). The same technique is used for P2 preambleinterleaving in DVB-T2.

L1 block of variable size can be used. Size can be adaptable to theamount of L1 signaling bits, resulting in a reduced overhead. Fullspectrum efficiency can be obtained with no PAPR issue. Less than 7.61MHz repetition can mean thatmore redundancy can be sent but unused. NoPAPR issue can arise because of 7.61 MHz repetition rate for L1 block.

FIG. 74 is another example of L1 signaling transmitted within a frameheader. This FIG. 74 is different from FIG. 70 in that the L1_span fieldhaving 12 bits it is divided into two fields. In other words, theL1_span field is divided into a L1_column having 9 bits and a L1_rowhaving 3 bits. The L1_column represents the carrier index that L1 spans.Because data slice starts and ends at every 12 carriers, which is thepilot density, the 12 bits of overhead can be reduced by 3 bits to reach9 bits.

L1_row represents the number of OFDM symbols where L1 is spanning whentime interleaving is applied. Consequently, time interleaving can beperformed within an area of L1_columns multiplied by L1_rows.Alternatively, a total size of L1 blocks can be transmitted such thatL1_span shown in FIG. 70 can be used when time interleaving is notperformed. For such a case, L1 block size is 11,776×2 bits in theexample, thus 15 bits is enough. Consequently, the L1_span field can bemade up of 15 bits.

FIG. 75 is an example of frequency or time interleaving/deinterleaving.The FIG. 75 shows a part of a whole transmission frame. The FIG. 75 alsoshows bonding of multiple 8 MHz bandwidths. A frame can consist of apreamble which transmits L1 blocks and a data symbol which transmitsdata. The different kinds of data symbols represent data slices fordifferent services. As shown in FIG. 75, the preamble transmits L1blocks for every 7.61 MHz.

For the preamble, frequency or time interleaving is performed within L1blocks and not performed between L1 blocks. That is, for the preamble,it can be said that interleaving is performed at L1 block level. Thisallows decoding the L1 blocks by transmitting L1 blocks within a tunerwindow bandwidth even when the tuner window has moved to a randomlocation within a channel bonding system.

For decoding data symbol at a random tuner window bandwidth,interleaving between data slices should not occur. That is, for dataslices, it can be said that interleaving is performed at data slicelevel. Consequently, frequency interleaving and time interleaving shouldbe performed within a data slice. Therefore, a symbol interleaver 308 ina data path of a BICM module of transmitter as shown in FIG. 37 canperform symbol interleaving for each data slice. A symbol interleaver308-1 in an L1 signal path can perform symbol interleaving for each L1block.

A frequency interleaver 403 shown in FIG. 42 needs to performinterleaving on the preamble and data symbols separately. Specifically,for the preamble, frequency interleaving can be performed for each L1block and for data symbol, frequency interleaving can be performed foreach data slice. At this point, time interleaving in data path or L1signal path may not be performed considering low latency mode.

FIG. 76 is a table analyzing overhead of L1 signaling which istransmitted in a FECFRAME header at the ModCod Header Inserting module307 on the data path of the BICM module as shown in FIG. 37. As seen inFIG. 76, for short LDPC block (size=16200), a maximum overhead of 3.3%can occur which may not be negligible. In the analysis, 45 symbols areassumed for FECFRAME protection and the preamble is a C2 frame specificL1 signaling and FECFRAME header is FECFRAME specific L1 signaling i.e.,Mod, Cod, and PLP identifier.

To reduce L1 overhead, approaches according to two Data-slice types canbe considered. For ACM/VCM type and multiple PLP cases, frame can bekept same as for the FECFRAME header. For ACM/VCM type and single PLPcases, the PLP identifier can be removed from the FECFRAME header,resulting in up to 1.8% overhead reduction. For CCM type and multiplePLP cases, the Mod/Cod field can be removed from the FECFRAME header,resulting in up to 1.5% overhead reduction. For CCM type and single PLPcases, no FECFRAME header is required, thus, up to 3.3% of overheadreduction can be obtained.

In a shortened L1 signaling, either Mod/Cod (7 bits) or PLP identifier(8 bits) can be transmitted, but it can be too short to get any codinggain. However, it is possible not to require synchronization becausePLPs can be aligned with the C2 transmission frame; every ModCod of eachPLP can be known from the preamble; and a simple calculation can enablesynchronization with the specific FECFRAME.

FIG. 77 is showing a structure for a FECFRAME header for minimizing theoverhead. In FIG. 77, the blocks with tilted lines and the FECFRAMEBuilder represent a detail block diagram of the ModCod Header Insertingmodule 307 on data path of the BICM module as shown in FIG. 37. Thesolid blocks represent an example of inner coding module 303, innerinterleaver 304, bit demux 305, and symbol mapper 306 on the data pathof the BICM module as shown in FIG. 37. At this point, shortened L1signaling can be performed because CCM does not require a Mod/Cod fieldand single PLP does not require a PLP identifier. On this L1 signal witha reduced number of bits, the LI signal can be repeated three times inthe preamble and BPSK modulation can be performed, thus, a very robustsignaling is possible. Finally, the ModCod Header Inserting module 307can insert the generated header into each FEC frame. FIG. 84 is showingan example of the ModCod extracting module r307 on the data path of BICMdemod module shown in FIG. 64.

As shown in FIG. 84, the FECFRAME header can be parsed (r301b), thensymbols which transmit identical information in repeated symbols can bedelayed, aligned, and then combined (Rake combining r302 b). Finally,when BPSK demodulation (r303b) is performed, received L1 signal fieldcan be restored and this restored L1 signal field can be sent to thesystem controller to be used as parameters for decoding. Parsed FECFRAMEcan be sent to the symbol demapper.

FIG. 78 is showing a bit error rate (BER) performance of theaforementioned L1 protection. It can be seen that about 4.8 dB of SNRgain is obtained through the a three time repetition. Required SNR is8.7 dB at BER=1E-11.

FIG. 79 is showing examples of transmission frames and FEC framestructures. The FEC frame structures shown on the upper right side ofthe FIG. 79 represent FECFRAME header inserted by the ModCod HeaderInserting module 307 in FIG. 37. It can be seen that depending onvarious combinations of conditions i.e.. CCM or ACM/VCM type and singleor multiple PLP, different size of headers can be inserted. Or, noheader can be inserted. Transmission frames formed according to dataslice types and shown on the lower left side of the FIG. 79 can beformed by the Frame header inserting module 401 of the Frame builder asshown in FIG. 42 and the merger/slicer module 208 of the input processorshown in FIG. 35. At this point, the FECFRAME can be transmittedaccording to different types of data slice. Using this method, a maximumof 3.3% of overhead can be reduced. In the upper right side of the FIG.79, four different types of structures are shown, but a skilled personin the art would understand that these are only examples, and any ofthese types or their combinations can be used for the data slice.

At the receiver side, the Frame header removing module r401 of the Frameparser module as shown in FIG. 63 and the ModCod extracting module r307of the BICM demod module shown in FIG. 64 can extract a ModCod fieldparameter which is required for decoding. At this point, according tothe data slice types of transmission frame parameters can be extracted.For example, for CCM type, parameters can be extracted from L1 signalingwhich is transmitted in the preamble and for ACM/VCM type, parameterscan be extracted from the FECFRAME header.

As shown in the upper right side of FIG. 79, the fecframe structure canbe divided into two groups, in which the first group is the upper threeframe structures with header and the second group is the last framestructure without header.

FIG. 80 is showing an example of L1 signaling which can be transmittedwithin the preamble by the Frame header inserting module 401 of theFrame builder module shown in FIG. 42. This L1 signaling is differentfrom the previous L1 signaling in that L1 block size can be transmittedin bits (L1 size, 14 bits); turning on/off time interleaving on dataslice is possible (dslice_time_intrlv, 1 bit); and by defining dataslice type (dslice_type, 1 bit), L1 signaling overhead is reduced. Atthis point, when the data slice type is CCM, the Mod/Cod field can betransmitted within the preamble rather than within the FECFRAME header(plp_mod (3 bits), plp_fec_type (1 bit), plp_cod (3 bits)).

At the receiver side, the shortened/punctured inner decoder r303-1 ofthe BICM demod as shown in FIG. 64 can obtain the first LDPC block,which has a fixed L1 block size, transmitted within the preamble,through decoding. The numbers and size of the rest of the LDPC blockscan also be obtained.

Time interleaving can be used when multiple OFDM symbols are needed forL1 transmission or when there is a time-interleaved data slice. Aflexible on/off of the time interleaving is possible with aninterleaving flag. For preamble time interleaving, a time interleavingflag (1 bit) and a number of OFDM symbols interleaved (3 bits) may berequired, thus, a total of 4 bits can be protected by a way similar to ashortened FECFRAME header.

FIG. 81 is showing an example of L1-pre signaling that can be performedat the ModCod Header Inserting module 307-1 on the data path of BICMmodule shown in FIG. 37. The blocks with tilted lines and PreambleBuilder are examples of the ModCod Header Inserting module 307-1 on theL1 signaling path of the BICM module shown in FIG. 37. The solid blocksare examples of the Frame header inserting module 401 of the Framebuilder as shown in FIG. 42.

Also, the solid blocks can be examples of shortened/punctured inner codemodule 303-1, inner interleaver 304-1, bit demux 305-1, and symbolmapper 306-1 on L1 signaling path of BICM module shown in FIG. 37.

As seen in FIG. 81, the L1 signal that is transmitted in the preamblecan be protected using shortened/punctured LDPC encoding. Relatedparameters can be inserted into the Header in a form of L1-pre. At thispoint, only time interleaving parameters can be transmitted in theHeader of the preamble. To ensure more robustness, a four timesrepetition can be performed. At the receiver side, to be able to decodethe L1 signal that is transmitted in the preamble, the ModCod extractingmodule r307-1 on the L1 signaling path of BICM demod as shown in FIG. 64needs to use the decoding module shown in FIG. 84. At this point,because there is a four times repetition unlike the previous decodingFECFRAME header, a Rake receiving process which synchronizes the fourtimes repeated symbols and adding the symbols, is required.

FIG. 82 shows a structure of L1 the signaling block that is transmittedfrom the Frame header inserting module 401 of the Frame builder moduleas shown in FIG. 42. It is showing a case where no time interleaving isused in a preamble. As shown in FIG. 82, different kind of LDPC blockscan be transmitted in the order of the carriers. Once an OFDM symbol isformed and transmitted then a following OFDM symbol is formed andtransmitted. For the last OFDM symbol to be transmitted, if there is anycarrier left, that carriers can be used for data transmission or can bedummy padded. The example in FIG. 82 shows a preamble that comprisesthree OFDM symbol. At a receiver side, for this non-interleaving case,the symbol deinterleaver r308-1 on the L1 signaling path of BICMdemodulator as shown in FIG. 64 can be skipped.

FIG. 83 shows a case where L1 time interleaving is performed. As shownin FIG. 83, block interleaving can be performed in a fashion of formingan OFDM symbol for identical carrier indices then forming an OFDMsymbols for the next carrier indices. As in the case where nointerleaving is performed, if there is any carrier left, that carrierscan be used for data transmission or can be dummy padded. At a receiverside, for this non-interleaving case, the symbol deinterleaver r308-1 onthe L1 signaling path of the BICM demodulator shown in FIG. 64 canperform block deinterleaving by reading LDPC blocks in increasing orderof numbers of the LDPC blocks.

In addition, there can be at least two types of data slices. Data slicetype 1 has dslice_type=0 in L1 signaling fields. This type of data slicehas no XFECFrame header and has its mod/cod values in L1 signalingfields. Data slice type 2 has dslice_type=1 in L1 signaling fields. Thistype of data slice has XFECFrame header and has its mod/cod values inXFECFrame header.

XFECFrame means XFEC(compleX Forward Error Correction)Frame and mod/codmeans modulation type/coderate.

At a receiver, a frame parser can form a frame from demodulated signals.The frame has data symbols and the data symbols can have a first type ofdata slice which has an XFECFrame and an XFECFrame header and a secondtype of data slice which has XFECFrame without XFECFrame header. Also, areceiver can extract a field for indicating whether to perform timede-interleaving on the preamble symbols or not to perform timede-interleaving on the preamble symbols, from the L1 of the preamblesymbols.

At a transmitter, a frame builder can build a frame. Data symbols of theframe comprise a first type of data slice which has an XFECFrame and anXFECFrame header and a second type of data slice which has XFECFramewithout XFECFrame header. In addition, a field for indicating whether toperform time interleaving on preamble symbols or not to perform timeinterleaving on preamble symbols can be inserted in L1 of the preamblesymbols.

Lastly, for shortened/punctured code for the Frame header insertingmodule 401 of the Frame builder shown in FIG. 42, a minimum size ofcodeword that can obtain coding gain can be determined and can betransmitted in a first LDPC block. In this manner, for the rest of LDPCblock sizes can be obtained from that transmitted L1 block size.

FIG. 85 is showing another example of L1-pre signaling that can betransmitted from ModCod Header Inserting module 307-1 on L1 signalinigpath of BICM module shown in FIG. 37. FIG. 85 is different from FIG. 81in that Header part protection mechanism has been modified. As seen inFIG. 85, L1 block size information L1_size (14 bits) is not transmittedin L1 block, but transmitted in Header. In the Header, time interleavinginformation of 4 bits can be transmitted too. For total of 18 bits ofinput, BCH (45, 18) code which outputs 45 bits are used and copied tothe two paths and finally, QPSK mapped. For the Q-path, 1 bit cyclicshift can be performed for diversity gain and PRBS modulation accordingto sync word can be performed. Total of 45 QPSK symbols can be outputfrom these I/Q path inputs. At this point, if time interleaving depth isset as a number of preambles that is required to transmit L1 block,L1_span (3 bits) that indicates time interleaving depth may not need tobe transmitted. In other words, only time interleaving on/off flag (1bit) can be transmitted. At a receiver side, by checking only a numberof transmitted preambles, without using L1_span, time deinterleavingdepth can be obtained.

FIG. 86 is showing an example of scheduling of L1 signaling block thatis transmitted in preamble. If a size of L1 information that can betransmitted in a preamble is Nmax, when L1 size is smaller than Nmax,one preamble can transmit the information. However, when L1 size isbigger than Nmax, L1 information can be equally divided such that thedivided L1 sub-block is smaller than Nmax, then the divided L1 sub-blockcan be transmitted in a preamble. At this point, for a carrier that isnot used because of L1 information being smaller than Nmax, no data aretransmitted.

Instead, as shown in FIG. 88, power of carriers where L1 block aretransmitted can be boosted up to maintain a total preamble signal powerequal to data symbol power. Power boosting factor can be varieddepending on transmitted L1 size and a transmitter and a receiver canhave a set value of this power boosting factor. For example, if only ahalf of total carriers are used, power boosting factor can be two.

FIG. 87 is showing an example of L1-pre signaling where power boostingis considered. When compared to FIG. 85, it can be seen that power ofQPSK symbol can be boosted and sent to preamble builder.

FIG. 89 is showing another example of ModCod extracting module r307-1 onL1 signalinig path of BICM demod module shown in FIG. 64. From inputpreamble symbol, L1 signaling FECFRAME can be output into symboldemapper and only header part can be decoded.

For input header symbol, QPSK demapping can be performed andLog-Likelihood Ratio (LLR) value can be obtained. For Q-path, PRBSdemodulation according to sync word can be performed and a reverseprocess of the 1-bit cyclic shift can be performed for restoration.

These aligned two I/Q path values can be combined and SNR gain can beobtained. Output of hard decision can be input into BCH decoder. The BCHdecoder can restore 18 bits of L1-pre from the input 45 bits.

FIG. 90 is showing a counterpart, ModCod extractor of a receiver. Whencompared to FIG. 89, power control can be performed on QPSK demapperinput symbols to restore from power level boosted by transmitter to itsoriginal value. At this point, power control can be performed byconsidering a number of carriers used for L1 signaling in a preamble andby taking an inverse of obtained power boosting factor of a transmitter.The power boosting factor sets preamble power and data symbol poweridentical to each other.

FIG. 91 is showing an example of L1-pre synchronization that can beperformed at ModCod extracting module r307-1 on L1 signaling path ofBICM demod module shown in FIG. 64. This is a synchronizing process toobtain a start position of Header in a preamble. Input symbols can beQPSK demapped then for the output Q-path, an inverse of 1 bit cyclicshift can be performed and alignment can be performed. Two I/Q pathsvalues can be multiplied and modulated values by L1-pre signaling can bede-modulated. Thus, output of multiplier can express only PRBS which isa sync word. When the output is correlated with a known sequence PRBS, acorrelation peak at Header can be obtained. Thus, a start position ofHeader in a preamble can be obtained. If necessary, power control whichis performed to restore original power level, as shown in FIG. 90, canbe performed on input of QPSK demapper.

FIG. 92 is showing another example of L1 block header field which issent to the Header Inserting module 307-1 on the L1 signaling path ofthe BICM module as shown in FIG. 37. This FIG. 92 is different from FIG.85 in that L1 _span which represents the time interleaving depth isreduced to 2 bits and reserved bits are increased by 1 bit. A receivercan obtain time interleaving parameter of L1 block from the transmittedL1_span.

FIG. 93 is showing processes of equally dividing a L1 block into as manyportions as a number of preambles then inserting a header into each ofthe divided L1 blocks and then assigning the header inserted L1 blocksinto a preamble. This can be performed when a time interleaving isperformed with a number of preambles where the number of preambles isgreater than a minimum number of preambles that is required fortransmitting L1 block. This can be performed at the L1 block on the L1signaling path of the BICM module as shown in FIG. 37. The rest of thecarriers, after transmitting L1 blocks can have cyclic repetitionpatterns instead of being zero padded.

FIG. 94 is showing an example of the Symbol Demapper r306-1 of the BICMdemod module as shown in FIG. 64. For a case where L1 FEC blocks arerepeated as shown in FIG. 93, each starting point of L1 FEC block can bealigned, combined (r301f), and then QAM demapped (r302f) to obtaindiversity gain and SNR gain. At this point, the combiner can includeprocesses of aligning and adding each L1 FEC block and dividing theadded L1 FEC block. For a case where only part of the last FEC block isrepeated as shown in FIG. 93, only the repeated part can be divided intoas many as a number of FEC block header and the other part can bedivided by a value which is one less than a number of FEC block header.In other words, the dividing number corresponds to a number of carriersthat is added to each carrier.

FIG. 98 is showing another example of L1 block scheduling. FIG. 98 isdifferent from FIG. 93 in that, instead of performing zero padding orrepetition when L1 blocks don t fill one OFDM symbol, OFDM symbol can befilled with parity redundancy by performing less puncturing onshortened/punctured code at the transmitter. In other words, when paritypuncturing (304 c) is performed at FIG. 38, the effective coderate canbe determined according to the puncturing ratio, thus, by puncturing asless bits have to be zero padded, the effective coderate can be loweredand a better coding gain can be obtained. The Parity de-puncturingmodule r303 a of a receiver as shown in FIG. 65 can performde-puncturing considering the less punctured parity redundancy. At thispoint, because a receiver and a transmitter can have information of thetotal L1 block size, the puncturing ratio can be calculated.

FIG. 95 is showing another example of L1 signaling field. FIG. 95 isdifferent from FIG. 74 in that, for a case where the data slice type isCCM, a start address (21 bits) of the PLP can be transmitted. This canenable FECFRAME of each PLP to form a transmission frame, without theFECFRAME being aligned with a start position of a transmission frame.Thus, padding overhead, which can occur when a data slice width isnarrow, can be eliminated. A receiver, when a data slice type is CCM,can obtain ModCod information from the preamble at the L1 signaling pathof the BICM demodulator as shown in FIG. 64, instead of obtaining itfrom FECFRAME header. In addition, even when a zapping occurs at arandom location of transmission frame, FECFRAME synchronization can beperformed without delay because the start address of PLP can be alreadyobtained from the preamble.

FIG. 96 is showing another example of L1 signaling fields which canreduce the PLP addressing overhead.

FIG. 97 is showing the numbers of QAM symbols that corresponds to aFECFRAME depending on the modulation types. At this point, a greatestcommon divisor of QAM symbol is 135, thus, an overhead of log2(135)≈7bits can be reduced. Thus, FIG. 96 is different from FIG. 95 in that anumber of PLP_start field bits can be reduced from 21 bits to 14 bits.This is a result of considering 135 symbols as a single group andaddressing the group. A receiver can obtain an OFDM carrier index wherethe PLP starts in a transmission frame after obtaining the PLP_startfield value and multiplying it by 135.

FIG. 99 and FIG. 101 show examples of symbol interleaver 308 which cantime interleave data symbols which are sent from the ModCod HeaderInserting module 307 on the data path of BICM module as shown in FIG.37.

FIG. 99 is an example of Block interleaver which can operate on adata-slice basis. The row value means a number of payload cells in fourof the OFDM symbols within one data-slice. Interleaving on OFDM symbolbasis may not be possible because the number of cells may change betweenadjacent OFDM cells. The column value K means a time interleaving depth,which can be 1, 2, 4, 8, or 16 . . . . Signaling of K for eachdata-slice can be performed within the L1 signaling. Frequencyinterleaver 403 as shown in FIG. 42 can be performed prior to timeinterleaver 308 as shown in FIG. 37.

FIG. 100 shows an interleaving performance of the time interleaver asshown in FIG. 99. It is assumed that a column value is 2, a row value is8, a data-slice width is 12 data cells, and that no continual pilots arein the data-slice. The top figure of FIG. 100 is an OFDM symbolstructure when time interleaving is not performed and the bottom figureof FIG. 100 is an OFDM symbol structure when time interleaving isperformed. The black cells represent scattered pilot and the non-blackcells represent data cells. The same kind of data cells represents anOFDM symbol. In FIG. 100, data cells that correspond to a single OFDMsymbol are interleaved into two symbols. An interleaving memory thatcorresponds to eight OFDM symbols is used but the interleaving depthcorresponds to only two OFDM symbols, thus, full interleaving depth isnot obtained.

FIG. 101 is suggested for achieving full interleaving depth. In FIG.101, the black cells represent scattered pilots and the non-black cellsrepresent data cells. Time interleaver as shown in FIG. 101 can beimplemented in a form of block interleaver and can interleavedata-slices. In FIG. 101, a number of column, K represents a data-slicewidth, a number of row, N represents time interleaving depth and thevalue, K can be random values i.e., K=1,2,3, . . . . The interleavingprocess includes writing data cell in a column twist fashion and readingin a column direction, excluding pilot positions. That is, it can besaid that the interleaving is performed in a row-column twisted fashion.

In addition, at a transmitter, the cells which are read in a columntwisted fashion of the interleaving memory correspond to a single OFDMsymbol and the pilot positions of the OFDM symbols can be maintainedwhile interleaving the cells.

Also, at a receiver, the cells which are read in a column twistedfashion of the de-interleaving memory correspond to a single OFDM symboland the pilot positions of the OFDM symbols can be maintained while timede-interleaving the cells.

FIG. 102 shows time interleaving performance of FIG. 101. For comparisonwith FIG. 99. it is assumed that a number of rows is 8, a data-slicewidth is 12 data cells, and that no continual pilots are in thedata-slice. In FIG. 102, data cells correspond to a single OFDM symbolare interleaved into eight OFDM symbols. As shown in FIG. 102, aninterleaving memory that corresponds to eight OFDM symbols is used andthe resulting interleaving depth corresponds to eight OFDM symbols,thus, full interleaving depth is obtained.

The time interleaver as shown in FIG. 101 can be advantageous in thatfull interleaving depth can be obtained using identical memory;interleaving depth can be flexible, as opposed to FIG. 99; consequently,a length of transmission frame can be flexible too, i.e., rows need notbe multiples of four. Additionally, the time interleaver used for dataslice, can be identical to the interleaving method used for the preambleand also can have commonality with a digital transmission system whichuses general OFDM. Specifically, the time interleaver 308 as shown inFIG. 37 can be used before the frequency interleaver 403 as shown inFIG. 42 is used. Regarding a receiver complexity, no additional memorycan be required other than additional address control logic which canrequire very small complexity.

FIG. 103 shows a corresponding symbol deinterleaver r308 in a receiver.It can perform deinterleaving after receiving output from the FrameHeader Removing module r401. In the deinterleaving processes, comparedto FIG. 99, the writing and reading processes of block interleaving areinverted. By using pilot position information, time deinterleaver canperform virtual deinterleaving by not writing to or reading from a pilotposition in the interleaver memory and by writing to or reading from adata cell position in the interleaver memory. Deinterleaved informationcan be output into the ModCod Extracting module r307.

FIG. 104 shows another example of time interleaving. Writing in diagonaldirection and reading row-by-row can be performed. As in FIG. 101,interleaving is performed taking into account the pilot positions.Reading and writing is not performed for pilot positions butinterleaving memory is accessed by considering only data cell positions.

FIG. 105 shows a result of interleaving using the method shown in FIG.104. When compared to FIG. 102, cells with the same patterns aredispersed not only in time domain, but also in the frequency domain. Inother words, full interleaving depth can be obtained in both time andfrequency domains.

FIG. 108 shows a symbol deinterleaver r308 of a corresponding receiver.The output of Frame Header Removing module r401 can be deinterleaved.When compared to FIG. 99, deinterleaving has switched the order ofreading and writing. Time deinterleaver can use pilot positioninformation to perform virtual deinterleaving such that no reading orwriting is performed on pilot positions but so that reading or writingcan be performed only on data cell positions. Deinterleaved data can beoutput into the ModCod Extracting module r307.

FIG. 106 shows an example of the addressing method of FIG. 105. NT meanstime interleaving depth and ND means data slice width. It is assumedthat a row value, N is 8, a data-slice width is 12 data cells, and nocontinual pilots are in data-slice. FIG. 106 represents a method ofgenerating addresses for writing data on a time interleaving memory,when a transmitter performs time interleaving. Addressing starts from afirst address with Row Address (RA)=0 and Column Address (CA)=0. At eachoccurrence of addressing, RA and CA are incremented. For RA, a modulooperation with the OFDM symbols used in time interleaver can beperformed. For CA, a modulo operation with a number of carriers thatcorresponds to a data slice width can be performed. RA can beincremented by 1 when carriers that correspond to a data slice arewritten on a memory. Writing on a memory can be performed only when acurrent address location is not a location of a pilot. If the currentaddress location is a location of a pilot, only the address value can beincreased.

In FIG. 106, a number of column, K represents the data-slice width, anumber of row, N represents the time interleaving depth and the value. Kcan be a random values i.e., K=1,2,3, . . . . The interleaving processcan include writing data cells in a column twist fashion and reading incolumn direction, excluding pilot positions. In other words, virtualinterleaving memory can include pilot positions but pilot positions canbe excluded in actual interleaving.

FIG. 109 shows deinterleaving, an inverse process of time interleavingas shown in FIG. 104. Writing row-by-row and reading in diagonaldirection can restore cells in original sequences.

The addressing method used in a transmitter can be used in a receiver.Receiver can write received data on a time deinterleaver memoryrow-by-row and can read the written data using generated address valuesand pilot location information which can be generated in a similarmanner with that of a transmitter. As an alternative manner, generatedaddress values and pilot information that were used for writing can beused for reading row-by-row.

These methods can be applied in a preamble that transmits L1. Becauseeach OFDM symbol which comprises preamble can have pilots in identicallocations, either interleaving referring to address values taking intoaccount the pilot locations or interleaving referring to address valueswithout taking into account the pilot locations can be performed. Forthe case of referring to address values without taking into account thepilot locations, the transmitter stores data in a time interleavingmemory each time. For such a case, a size of memory required to performinterleaving/deinterleaving preambles at a receiver or a transmitterbecomes identical to a number of payload cells existing in the OFDMsymbols used for time interleaving.

FIG. 107 is another example of L1 time interleaving. In this example,time interleaving can place carriers to all OFDM symbols while thecarriers would all be located in a single OFDM symbol if no timeinterleaving was performed. For example, for data located in a firstOFDM symbol, the first carrier of the first OFDM symbol will be locatedin its original location. The second carrier of the first OFDM symbolwill be located in a second carrier index of the second OFDM symbol. Inother words, i-th data carrier that is located in n-th OFDM symbol willbe located in an i-th carrier index of (i+n) mod N th OFDM symbol, wherei=0, 1, 2 number of carrier-1, n=0, 1, 2, N−1, and N is a number of OFDMsymbols used in L1 time interleaving. In this L1 time interleavingmethod, it can be said that interleaving for all the OFDM symbols areperformed a twisted fashion as shown in FIG. 107. Even though pilotpositions are not illustrated in FIG. 107, as mentioned above,interleaving can be applied to all the OFDM symbols including pilotsymbols. That is, it can be said that interleaving can be performed forall the OFDM symbols without considering pilot positions or regardlessof whether the OFDM symbols are pilot symbols or not.

If a size of a LDPC block used in L1 is smaller than a size of a singleOFDM symbol, the remaining carriers can have copies of parts of the LDPCblock or can be zero padded. At this point, a same time interleaving asabove can be performed. Similarly, in FIG. 107, a receiver can performdeinterleaving by storing all the blocks used in L1 time interleaving ina memory and by reading the blocks in the order in which they have beeninterleaved, i.e., in order of numbers written in blocks shown in FIG.107.

When a block interleaver as shown in FIG. 106 is used, two buffers areused.

Specifically, while one buffer is storing input symbols, previouslyinput symbols can be read from the other buffer. Once these processesare performed for one symbol interleaving block, deinterleaving can beperformed by switching order of reading and writing, to avoid memoryaccess conflict. This ping-pong style deinterleaving can have a simpleaddress generation logic. However, hardware complexity can be increasedwhen using two symbol interleaving buffers.

FIG. 110 shows an example of a symbol deinterleaver r308 or r308-1 asshown in FIG. 64. This proposed embodiment of the invention can use onlya single buffer to perform deinterleaving. Once an address value isgenerated by the address generation logic, the address value can beoutput from the buffer memory and in-placement operation can beperformed by storing a symbol that is input into the same address. Bythese processes, a memory access conflict can be avoided while readingand writing. In addition, symbol deinterleaving can be performed usingonly a single buffer. Parameters can be defined to explain this addressgeneration rule. As shown in FIG. 106, a number of rows of adeinterleaving memory can be defined as time interleaving depth, D and anumber of columns of the deinterleaving memory can be defined as dataslice width, W. Then the address generator can generate the followingaddresses.

i-th sample on j-th block, including pilot

i=0,1,2, . . . , N−1;

N=D*W;

Ci,j=i mod W;

Tw=((Ci,j mod D)*j)mod D;

Ri,j=((i div W)+Tw)mod D;

Li,j(1)=Ri,j*W+Ci,j;

Or

Li,j(2)=Ci,j*D+Ri,j;

The addresses include pilot positions, thus, input symbols are assumedto include pilot positions. If input symbols that include only datasymbols need to be processed, additional control logic which skips thecorresponding addresses can be required. At this point, i represents aninput symbol index, j represents an input interleaving block index, andN=D*W represents an interleaving block length. Mod operation representsmodulo operation which outputs remainder after division. Div operationrepresents division operation which outputs quotient after division.Ri,j and Ci,j represent row address and column address of i-th symbolinput of j-th interleaving block, respectively. Tw represents columntwisting value for addresses where symbols are located. In other words,each column can be considered as a buffer where independent twisting isperformed according to Tw values. Li,j represents an address when singlebuffer is implemented in an one dimension sequential memory, not in twodimension. Li,j can have values from 0 to (N−1). Two different methodsare possible. Li,j(1) is used when the memory matrix is connectedrow-by-row and Li,j(2) is used when the memory matrix is connected incolumn-by-column.

FIG. 111 shows an example of row and column addresses for timedeinterleaving when D is 8 and W is 12. J starts from j=0 and for each jvalue, a first row can represent the row address and a second row canrepresent the column address. The FIG. 111 shows only addresses of thefirst 24 symbols. Each column index can be identical to the input symbolindex i.

FIG. 113 shows an example of an OFDM transmitter using a data slice. Asshown in FIG. 113, the transmitter can comprise a data PLP path, an L1signaling path, a frame builder, and an OFDM modulation part. The dataPLP path is indicated by blocks with horizontal lines and verticallines. The L1 signaling path is indicated by blocks with tilted lines.Input process modules 701-0, 701-N, 701-K, and 701-M can comprise blocksand sequences of input interface module 202-1, input streamsynchronizing module 203-1, delay compensation module 204-1, null packetdeletion module 205-1, CRC encoder 206-1, BB header inserting module207-1, and BB scrambler 209 performed for each PLP as shown in FIG. 35.FEC modules 702-0, 702-N, 702-K, and 702-M can comprise blocks andsequences of outer coder 301 and inner coder 303 as shown in FIG. 37. AnFEC modules 702-L1 used on the L1 path can comprise blocks and sequencesof outer coder 301-1 and shortened/punctured inner coder 303-1 as shownin FIG. 37. L1 signal module 700-L1 can generate L1 information requiredto comprise a frame.

Bit interleave modules 703-0, 703-N, 703-K, and 703-M can compriseblocks and sequences of inner interleaver 304 and bit demux 305 as shownin FIG. 37. Bit interleaver 703-L1 used on the L1 path can compriseblocks and sequences of inner interleaver 304-1 and bit demux 305-1 asshown in FIG. 37. Symbol mapper modules 704-0, 704-N, 704-K, and 704-Mcan perform functions identical with the functions of the symbol mapper306 shown in FIG. 37. The symbol mapper module 704-L1 used on L1 pathcan perform functions identical with the functions of the symbol mapper306-1 shown in FIG. 37. FEC header modules 705-0, 705-N, 705-K, and705-M can perform functions identical with the functions of the ModCodHeader inserting module 307 shown in FIG. 37. FEC header module 705-L1for the L1 path can perform functions identical with the functions ofthe ModCod Header inserting module 307-1 shown in FIG. 37.

Data slice mapper modules 706-0 and 706-K can schedule FEC blocks tocorresponding data slices and can transmit the scheduled FEC blocks,where the FEC blocks correspond to PLPs that are assigned to each dataslice. Preamble mapper 707-L1 block can schedule L1 signaling FEC blocksto preambles. L1 signaling FEC blocks are transmitted in preambles. Timeinterleaver modules 708-0 and 708-K can perform functions identicalwiththe functions of the symbol interleaver 308 shown in FIG. 37 whichcan interleave data slices. Time interleaver 708-L1 used on L1 path canperform functions identical with the functions of the symbol interleaver308-1 shown in FIG. 37.

Alternatively, time interleaver 708-L1 used on L1 path can performidentical functions with symbol interleaver 308-1 shown in FIG. 37, butonly on preamble symbols.

Frequency interleavers 709-0 and 709-K can perform frequencyinterleaving on data slices. Frequency interleaver 709-L1 used on L1path can perform frequency interleaving according to preamble bandwidth.

Pilot generating module 710 can generate pilots that are suitable forcontinuous pilot

(CP), scattered pilot (SP), data slice edge, and preamble. A frame canbe built (711) from scheduling the data slice, preamble, and pilot. TheIFFT module 712 and GI inserting module 713 blocks can perform functionsidentical with the functions of the IFFT module 501 and the GI insertingmodule 503 blocks shown in FIG. 51, respectively. Lastly, DAC module 714can convert digital signals into analog signals and the convertedsignals can be transmitted.

FIG. 114 shows an example of an OFDM receiver which uses data slice. InFIG. 114, tuner r700 can perform the functions of the tuner/AGC moduler603 and the functions of the down converting module r602 shown in FIG.61. ADC r701 can convert received analog signals into digital signals.Time/freq synchronizing module r702 can perform functions identical withthe functions of the time/freq synchronizing module r505 shown in FIG.62. Frame detecting module r703 can perform functions identical with thefunctions of the frame detecting module r506 shown in FIG. 62.

At this point, after time/frequency synchronization are performed,synchronization can be improved by using preamble in each frame that issent from frame detecting module r703 during tracking process.

GI removing module r704 and FFT module r705 can perform functionsidentical with the functions of the GI removing module r503 and the FFTmodule r502 shown in FIG. 62, respectively.

Channel estimation module r706 and channel Equalization module r707 canperform a channel estimation part and a channel equalization part of thechannel Est/Eq module r501 as shown in FIG. 62. Frame parser r708 canoutput a data slice and preamble where services selected by a user aretransmitted. Blocks indicated by tilted lines process a preamble. Blocksindicated by horizontal lines which can include common PLP, process dataslices. Frequency deinterleaver r709-L1 used on the L1 path can performfrequency deinterleaving within the preamble bandwidth. Frequencydeinterleaver r709 used on the data slice path can perform frequencydeinterleaving within data slice. FEC header decoder r712-L1, timedeinterleaver r710-L1, and symbol demapper r713-L1 used on the L1 pathcan perform functions identical with the functions of the ModCodextracting module r307-1, symbol deinterleaver r308-1, and symboldemapper r306-1 shown in FIG. 64.

Bit deinterleaver r714-L1 can comprise blocks and sequences of bit demuxr305-1 and inner deinterleaver r304-1 as shown in FIG. 64. FEC decoderr715-L1 can comprise blocks and sequences of shortened/punctured innercoder r303-1 and outer decoder r301-1 shown in FIG. 64. At this point,the output of the L1 path can be L1 signaling information and can besent to a system controller for restoring PLP data that are transmittedin data slices.

Time deinterleaver r710 used on the data slice path can performfunctions identical with the functions of the symbol deinterleaver r308shown in FIG. 64. Data slice parser r711 can output user selected PLPfrom the data slices and, if necessary, common PLP associated with theuser selected PLP. FEC header decoders r712-C and r712-K can performfunctions identical with the functions of the ModCod extracting moduler307 shown in FIG. 64. Symbol demappers r713-C and r713-K can performfunctions identical with the functions of the symbol demapper r306 shownin FIG. 64.

Bit deinterleaver r714-C and r714-K can comprise blocks and sequences ofbit demux r305 and inner deinterleaver r304 as shown in FIG. 64. FECdecoders r715-C and r715-K can comprise blocks and sequences of innerdecoder r303 and outer decoder r301 as shown in FIG. 64. Lastly, outputprocess modules r716-C and r716-K can comprise blocks and sequences ofBB descrambler r209, BB header removing module r207-1, CRC decoderr206-1, null packet inserting module r205-1, delay recover r204-1,output clock recover r203-1, and an output interface r202-1 which areperformed for each PLP in FIG. 35. If a common PLP is used, the commonPLP and data PLP associated with the common PLP can be transmitted to aTS recombiner and can be transformed into a user selected PLP.

It should be noted from FIG. 114, that in a receiver, the blocks on theL1 path are not symmetrically sequenced to a transmitter as opposed tothe data path where the blocks are symmetrically positioned or inopposite sequence of a transmitter. In other words, for the data path,Frequency deinterleaver r709, Time deinterleaver r710, Data slice parserr711, and FEC header decoder r712-C and r712-K are positioned. However,for the L1 path, Frequency deinterleaver r709-L1, FEC header decoderr712-L1, and time deinterleaver r710-L1 are positioned.

FIG. 112 shows an example of general block interleaving in a data symboldomain where pilots are not used. As seen from FIG. 112 a, interleavingmemory can be filled without black pilots. To form a rectangular memory,padding cells can be used if necessary. In FIG. 112 a, padding cells areindicated as cells with tilted lines. In the example, because onecontinual pilot can overlap with one kind of scattered pilot pattern, atotal of three padding cells are required during four of OFDM symbolduration. Finally, in FIG. 112 b, interleaved memory contents are shown.

As in FIG. 112 a, either writing row-by-row and performing columntwisting; or writing in a twisted fashion from the beginning, can beperformed. Output of the interleaver can comprise reading row-by-rowfrom memory. The output data that has been read can be placed as shownin FIG. 112 c when OFDM transmission is considered. At this time, forsimplicity, frequency interleaving can be ignored. As seen in FIG. 112,frequency diversity is not as high as that of FIG. 106, but ismaintained at a similar level. Most of all, it can be advantageous inthat the memory required to perform interleaving and deinterleaving canbe optimized. In the example, memory size can be reduced from W*D to(W−1)*D. As the data slice width becomes bigger, the memory size can befurther reduced.

For time deinterleaver inputs, a receiver should restore memory buffercontents in a form of the middle figure of FIG. 112 while consideringpadding cells. Basically, OFDM symbols can be read symbol-by-symbol andcan be saved row-by-row. De-twisting corresponding to column twistingcan then be performed. The output of the deinterleaver can be output ina form of reading row-by-row from the memory of the FIG. 112 a. In thisfashion, when compared to the method shown in FIG. 106, pilot overheadcan be minimized, and consequently interleaving/deinterleaving memorycan be minimized.

Using the suggested methods and devices, among others advantages it ispossible to implement an efficient digital transmitter, receiver andstructure of physical layer signaling.

By transmitting ModCod information in each BB frame header that isnecessary for ACM/VCM and transmitting the rest of the physical layersignaling in a frame header, signaling overhead can be minimized.

Modified QAM for a more energy efficient transmission or a morenoise-robust digital broadcasting system can be implemented. The systemcan include transmitter and receiver for each example disclosed and thecombinations thereof.

An Improved Non-uniform QAM for a more energy efficient transmission ora more noise-robust digital broadcasting system can be implemented. Amethod of using code rate of error correction code of NU-MQAM and MQAMis also described. The system can include transmitter and receiver foreach example disclosed and the combinations thereof.

The suggested L1 signaling method can reduce overhead by 3-4% byminimizing signaling overhead during channel bonding.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the invention.

What is claimed is:
 1. A transmitter for transmitting at least onebroadcast signal having PLP (Physical Layer Pipe) data, the transmittercomprising: a BCH (Bose-Chadhuri-Hocquenghem) encoder configured to BCHencode the PLP data; an LDPC (Low Density Parity Check) encoderconfigured to LDPC encode the BCH encoded PLP data and output FECFrames(Forward Error Correction Frames), wherein the PLP data are processed byan LDPC scheme for a long LDPC FECframe or a short LDPC FECframe; amapper configured to map data in the FECFrames onto constellations byQAM (Quadrature Amplitude Modulation) schemes; a time-interleaverconfigured to time-interleave the mapped data; a frame builderconfigured to build a signal frame including preamble symbols and datasymbols, wherein the preamble symbols include signaling information forthe time-interleaved PLP data, and wherein the data symbols include thetime-interleaved PLP data; and an OFDM (Orthogonal Frequency DivisionMultiplexing) modulator configured to modulate data in the signal frameby an OFDM scheme.
 2. The transmitter of claim 1, wherein the signalinginformation is repeated in the preamble symbols.
 3. The transmitter ofclaim 1, wherein the signaling information includes PLP ID informationidentifying each of the PLP data and FEC type information indicating theLDPC scheme for the long LDPC FECframe or the short LDPC FECframe. 4.The transmitter of claim 1, further comprising: a second BCH encoderconfigured to BCH encode the signaling information; and a second LDPCencoder configured to LDPC encode the BCH encoded signaling information.5. A method of transmitting at least one broadcast signal having PLP(Physical Layer Pipe) data, the method comprising: BCH(Bose-Chadhuri-Hocquenghem) encoding the PLP data; LDPC (Low DensityParity Check) encoding the BCH encoded PLP data to output FECFrames(Forward Error Correction Frames), wherein the PLP data are processed byan LDPC scheme for a long LDPC FECframe or a short LDPC FECframe;mapping data in the FECFrames onto constellations by QAM (QuadratureAmplitude Modulation) schemes; time-interleaving the mapped data;building a signal frame including preamble symbols and data symbols,wherein the preamble symbols include signaling information for thetime-interleaved PLP data, and wherein the data symbols include thetime-interleaved PLP data; and modulating data in the signal frame by anOFDM (Orthogonal Frequency Division Multiplexing) scheme.
 6. The methodof claim 5, wherein the signaling information is repeated in thepreamble symbols.
 7. The method of claim 5, wherein the signalinginformation includes PLP ID information identifying each of the PLP dataand FEC type information indicating the LDPC scheme for the long LDPCFECframe or the short LDPC FECframe.
 8. The method of claim 5, furthercomprising: BCH encoding the signaling information; and LDPC encodingthe BCH encoded signaling information.
 9. A receiver for receiving atleast one broadcast signal having PLP (Physical Layer Pipe) data, thereceiver comprising: an OFDM (Orthogonal Frequency DivisionMultiplexing) demodulator configured to demodulate the at least onebroadcast signal by an OFDM scheme; a frame parser configured to parse asignal frame in the demodulated at least one broadcast signal, whereinthe signal frame includes preamble symbols and data symbols, and whereinthe preamble symbols include signaling information for the PLP data; atime-deinterleaver configured to time-deinterleave data in the datasymbols; a demapper configured to demap the time-deinterleaved data byQAM (Quadrature Amplitude Modulation) schemes to output FECFrames(Forward Error Correction Frames); an LDPC (Low Density Parity Check)decoder configured to LDPC decode data in the FECFrames, wherein thedata in the FECFrames are processed by an LDPC scheme for a long LDPCFECframe or a short LDPC FECframe; and a BCH (Bose-Chadhuri-Hocquenghem)decoder configured to BCH decode the LDPC decoded data to output the PLPdata.
 10. The receiver of claim 9, wherein the signaling information isrepeated in the preamble symbols.
 11. The receiver of claim 9, whereinthe signaling information includes PLP ID information identifying eachof the PLP data and FEC type information indicating the LDPC scheme forthe long LDPC FECframe or the short LDPC FECframe.
 12. The receiver ofclaim 9, further comprising: a second LDPC decoder configured to LDPCdecode the signaling information; and a second BCH decoder configured toBCH decode the LDPC decoded signaling information.
 13. A method ofreceiving at least one broadcast signal having PLP (Physical Layer Pipe)data, the method comprising: demodulating the at least one broadcastsignal by an OFDM (Orthogonal Frequency Division Multiplexing) scheme;parsing a signal frame in the demodulated at least one broadcast signal,wherein the signal frame includes preamble symbols and data symbols, andwherein the preamble symbols include signaling information for the PLPdata; time-deinterleaving data in the data symbols; demapping thetime-deinterleaved data by QAM (Quadrature Amplitude Modulation) schemesto output FECFrames (Forward Error Correction Frames); LDPC (Low DensityParity Check) decoding data in the FECFrames, wherein the data in theFECFrames are processed by an LDPC scheme for a long LDPC FECframe or ashort LDPC FECframe; and BCH (Bose-Chadhuri-Hocquenghem) decoding theLDPC decoded data to output the PLP data.
 14. The method of claim 13,wherein the signaling information is repeated in the preamble symbols.15. The method of claim 13, wherein the signaling information includesPLP ID information identifying each of the PLP data and FEC typeinformation indicating the LDPC scheme for the long LDPC FECframe or theshort LDPC FECframe.
 16. The method of claim 13, further comprising:LDPC decoding the signaling information; and BCH decoding the LDPCdecoded signaling information.